The first, the old timer mechanism, has a static array of 32 pointers to timer_struct data structures and a mask of active timers, timer_active. Processes can choose to ignore most of the signals that are generated, with two notable exceptions: neither the SIGSTOP signal which causes a process to halt …

It links the sock data structure to the BSD socket data structure using the data pointer in the BSD socket. The GNU C library provides more than its name suggests. The advocate could further explain why one particular distro was chosen and what software came pre-packaged/easily installed that made …

Because Linux has such a large number of contributors from across multiple decades of development, contacting each individual author and getting them to agree to a new license is virtually impossible, so that Linux remaining licensed under the GPLv2 in perpetuity is all but assured. They prefer the term open …

Open Source software, like its name suggests, provides users with an open code that can be freely used, modified, and shared by everyone. The so-called open source and free software development models started with the Free Software Foundation and were popularized with Linux. Each filesystem is mounted to a specific …

If you find a bug, report it! The format most common in Linux is called Executable and Linkable Format (ELF). But all things come to an end eventually. You would want that file access to be strictly coordinated.

How much do you know about the Linux rlogin command?

You can pick up a book on Unix from the '80s and much of it will still be applicable to a modern Linux distribution today. Linux provides any tools you need as a developer to operate a scalable, secure servers. When TCP transmits its packet using IP, the data contained …

Libraries were written and ported, filesystems developed, and hardware drivers written for many popular devices. An exit status of zero indicates success. Tied closely to IoT is the drone trend, that of remotely controlled flying robots. A character device is accessed as a linear queue of bytes.

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That is, they do not require that the source code be included with redistributions of modified versions of programs that use such licenses. Also, the lack of a common kernel within Unix distributions has implications for software and hardware vendors. Software is not some mystic magic which must be locked …

Most of the malware are propagated through the Internet. You might also wonder whether ext4 is still in active development at all, given the flurries of news coverage of alternate filesystems such as btrfs, xfs, and zfs. It is sad to see that people today actually have to use the …

The GPL subsequently became by far the most widely used license for free software. Currently, in Distrowatch's past 6 months ranking, it sits at #3. Linux is a topic which is equally suitable for study in the classroom (such as at a university or a specialized computer school) or at …

Specific filesystems, however, may impose their own restrictions, imposing a smaller ceiling on the maximum length. It is not possible to directly link user-space applications with kernel space. In many ways, Linux and UNIX administration is today much easier than administration for popular commercial personal operating systems because it is …

Linux protects against this by maintaining lists of adjustments to the semaphore arrays. There are three types of partition supported by fdisk, primary, extended and logical. The first filesystem mounted is located in the root of the namespace, /, and is called the root filesystem. It doesn't take long to realize …

Most recently, the U.S. Whereas it had previously been the norm to assist colleagues and freely share ideas and software, such cooperation suddenly became forbidden and was made a crime. But this book, like most texts on system programming, is unconcerned with kernel development. Linux is a popular platform …

Keep in mind that these are only conventions---not rules. You can easily see the exported kernel symbols and their values by looking at /proc/ksyms or by using the ksyms utility. Traditionally, Unix programs have been single-threaded, owing to Unix's historic simplicity, fast process creation times, and robust IPC mechanisms …

After moving the Linux I've noticed a dramatic improvement in the speed and performance of my work flow, with the exact same tools I used on Windows. What does this mean to you? Each individual semaphore operation may request that an adjustment be maintained. The Free Software Movement would be …

Without this surrounding commitment, IT decision-makers can be left in the dark...and that's not a good place to be in 2019. Device drivers have to be careful when using memory. The character % introduces a job name. Writing a byte to a file position beyond the end of the file …

The world economy will not collapse if creators of software choose to share their work with the world. When adding a user to a system you will be asked for your root i.d. In all of the cases above, the synergy created between the pairs has only gone to …

It is as old as computers themselves. As the information age went on, though, corporations became progressively more obsessed with controlling the spread of knowledge. The boom in interest around the Internet of Things (IoT), the notion of a network of devices, big and small, that can "talk" to each …

By contrast, most software carries fine print that denies users these basic rights, leaving them susceptible to the whims of its owners and vulnerable to surveillance. There is no problem with using an older computer, for example, an elderly 500MHz Pentium PC with as few as five gigabytes of hard …

A server is a computer with an operating system that is configured to allow other computers to connect to it from across a network. This is one of those arguments that sounds good superficially but which is not borne out by the evidence. If you plan to incorporate such software …

Physical filesystems reside on block storage devices, such as CDs, floppy disks, compact flash cards, or hard drives. Today open source software has become critical for almost every organization. If you love the rolling Linux distributions (here are some fixed vs rolling release differences), then you don't need to look …

Each device driver tells the operating system how to use that specific device. The process tree is rooted at the first process, known as the init process, which is typically the init program. By and throughout the 1990s, you could find MINIX installations thriving in universities worldwide-and a young Linus …

No distribution of Linux is completely bug-free, so you may be required to fix small problems by hand after installation. Keep in mind that these are only conventions---not rules. There are Web sites, articles, and books devoted to the subject, and Linux User Groups (also known as LUGs) meet in …

From the filename, the kernel obtains the inode number. The command cd may be run without a location as we saw in the shortcut above but usually will be run with a single command line argument which is the location we would like to change into. A block device cannot …

Initially, there is only one directory on the disk, the root directory. But note that this book does not cover the Linux programming environment -for example, there is no tutorial on make in these pages. The count is the number of kernel entities that are dependent on this module. In …

By opening the code to widespread examination, more people take part in finding its bugs and security flaws, in testing for broad compatibility across platforms, and in providing new ideas. This means that when the next process that attempts to access this memory gets a page fault, the shared memory …

In this way, the Internet acts as the glue that binds together Linux developers in particular and OSS developers in general. Built in to the structure of the command-line environment are dozens of commands and several text-based help systems. Now, imagine that the execution of all the above commands is …

However, this is no less "programming" than anything else. On these foundationless grounds, what would be the problem with using Skype and locking not only yourself, but also all of your friends, into one company's software and protocol? It uses YUM for package management. A host wishing to know the …

Linux is a popular platform for everything from middleware to embedded computing and clusters, to parallel supercomputers and gadgets. Anyone who knows what they are doing is welcome to develop for the core, and submit patches. All controllers are different, but they usually have registers which control them. A block …

Whenever we refer to a file or directory we are using one of these paths. Popular distributions include Debian, Fedora, Mint, and Ubuntu, but there are many others. The CPU can access both the system space memory and the I/O space memory, whereas the controllers themselves can only access …

The access file logs every visit to your web site. For example, a processor could execute an instruction every clock pulse. A way to prevent that is regular updates and only download software, themes and plugns form reliable sources. It looks at each member of the operations pending queue (sem_pending …

Because Linux has such a large number of contributors from across multiple decades of development, contacting each individual author and getting them to agree to a new license is virtually impossible, so that Linux remaining licensed under the GPLv2 in perpetuity is all but assured. Linux tracks the usage of …

The issues with the Diebold [2] voting systems in the US is testament [3] to the need for transparent systems that are trustworthy. In the above example, the vfat and msdos modules are both dependent on the fat module and so it has a count of 2. For Linux, a …

Therefore, an alias definition appearing on the same line as another command does not take effect until the next line of input is read. Let's face it; Windows OS is vulnerable to different types of attacks (or hacks). Grep will take the output for that command, which is the name …

Linux is open-source. With all the activity around Unix at Berkeley, a new delivery of Unix software was born: the Berkeley Software Distribution, or BSD. Furthermore, the developer writing Python or Ruby or Scala can still benefit from knowledge of system programming, as an understanding of the soul of the …

Public domain refers to the total absence of copyright protection. Normally, Linux would suspend the requestor, putting the process onto a wait queue until there is enough physical memory. It sounds counterintuitive and/or just plain stupid on paper, but is generally seen as the traditional and conservative way to …

In addition to the real uid, each process also has an effective uid, a saved uid, and a filesystem uid. The terminal in Linux is a wild card. Whereas sockets communicating over the Internet might use a hostname and port pair for identifying the target of communication, Unix domain sockets …